14-3 MOKPEQLOGY AND EVOLUTION
ligainenfcum teres is connected to the strong shaft by a comparatively slender neck; but the angle between them is not so wide as in the Orang. The trochanters are well marked, and the great trochanter reaches up to the level of the junction of the upper and middle thirds of the head. The shaft is slightly bent, but the linea aspera is variable. The internal condyle is wide, with an adductor
tubercle ; and the external cond}rle. whose articular surface is directed downwards and inwards, forms a semicircle, which is not suitable for acting as a supporting agent like the more flattened condyle in Man. In the Gorilla the femur is shorter than in Man, and the neck is less oblique. The angle between the neck and shaft is 124", whereas it is 128° to 141° in Man (Duckworth). The great trochanter rises up to the level to the top of the head. The small trochanter is farther from the great trochanter than in Man. The linea aspera is absent or poor, and confined to the upper half of the shaft, and the lower part of the shaft expands more gradually to the condyles than in Man. In the Orang there is no pit for the ligainentum teres.
The characters of the lower end of the femur are of great importance. The external condyle is larger than the inner one in man, but the reverse is the case in the Gorilla, Chimpanzee and Gibbon. The internal condyle reaches lower down than the outer one in Man, the Chimpanzee and Gibbon, but the outer one is lower in the Gorilla.
The Tibia and Fibula.—In the Gibbons the tibia is slightly curved, and the extremities of the fibula are almost equal In the Chimpanzee the head of the tibia is relatively larger than in Man, and is inclined slightly